Gaseous electric discharge device



April 25, 1933. G. ZECHER GASEOUS ELECTRIC DISCHARGE DEVICE Filed July 22, 1932 INVENTOR ATTORNEY Patented Apr 25, 1933 warren STA PATENT OFFICE GUSTAV ZECH ER, OF EIN'DHOVEN, NETHERLANDS, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK GASEOUS ELECTRIC DISCHARGE DEVICE Application filed July 22, 1932, Serial No. 624,126, and in the Netherlands July 25, 1931.

The present invention relates to gaseous electric discharge devices generally and more particularly the invention relates to methods and means for starting and operating such devices.

It is now known in the art thatgaseous Y electric discharge devices having one or more thermionic electrodes have a negative volt-.

ampere characteristic which necessitates a stabilizing impedance connected in series with the electric discharge device. Such stabilizing devices have an appreciable current consumption which lowers the efiiciency of the electric discharge device.

The object of the present invention is to provide a method of and a means for starting and operating gaseous electric discharge devices in which the customary separate impedance device is eliminated. Anotherobject of the invention is to increase the operating efiiciency of gaseous electric discharge devices. Further objects and advantages attaching to the device and to its use and operation will be apparent to those skilled in the art from the following particular description and from the appended claims.

The invention attains its objects by connecting the primary coil of a transformer in series with the discharge path in the elec tric discharge device and said transformer has one or more secondary coils which supply the heating current for one or more thermionic electrodes of the electric discharge device, said electrodes are, when.

desired, of the well known equi-potential cathode type. The primary coil of the transformer thus acts as the series impedance for the electric discharge device. The electrical energy in the primary coil of the transformer, connected in series with the discharge path in the electric discharge device, is thus used as the heating current for the thermionic cathode instead of being consumed in the separate impedance device as heretofore. Further, a separate transformer is not required for the supply of the heating current to the thermionic cathode which effects a saving in material. here desired an impedance (resistance, self-inductance or capacitance) may be connected in series with the tube in addition to the primary coil of the transformer. 1

When this device is connected to the current source, a glow discharge, in some cases, occurs between the originally cold electrodes.

The glow-discharge current flows through the seriesconnected primary coil of the transformer whereby a current is induced in the secondary coil of said transformer which current heats the thermionic cathode to an electron emitting temperature so that the electric discharge changes into an electric-arc discharge. when desired, is of such len th that a positive column is present in the electric discharge device along with the arc discharge.

When the glow discharge current flowing through the primary coil is too weak to develop a sufficiently heavy current in the sec ondary coil, or when a glow discharge does not take place at all, the starting ofthe electric discharge is facilitated by connecting the discharge path in parallel with a circuit in which. a current interrupter is provided. When the interrupter is closed, the discharge path is short-circuited and suiiicient current flows through the primary coil of the transformer to heat the thermionic electrode to the required temperature. When the interrupter is opened, the discharge path is no longer short circuited and the electric discharge between the electrodes in the tube is established.

The discharge path,

The invention is applicable to discharge tubes with two thermionic electrodes which act alternately as cathode and anode, or to tubes with more than two thermionic electrodes and also to two discharge tubes with one thermionic cathode and one or more cold anodes. 1

When two or more discharge tubes with two thermionic electrodes are connected in parallel it is advantageous to heat one of the thermionic electrodes of each of the tubes by means of a separate transformer, while eac of the other thermionic electrodes of the discharge tubes are heated by means of the secondary coil of the transformer for the electric discharge device the primary coil of which is connected in series with the electric discharge device. When the electric discharge device contains two thermionic electrodes, it is also possible to heat one of said electrodes by means of a separate transformer. When thedevice is started into operation, it is desirable that the electrode connected to the separate transformer be heated first in order to facilitate the formation of a glow discharge on the other electrode.

Where the discharge device is provided] with a thermionic cathode and two or more cold anodes, it is preferable to connect the primary coil of a transformer between each anode and the current source on which the tube is operated, and said primary coil is designed in such a way that an alternating cu1= rent is induced in one of the secondary coils of the transformer which current heats the thermionic cathode.

The invention is applicable to discharge devices with directly heated electrodes and to devices with indirectly heated electrodes.

Vfherever a gas filled electric discharge de-. vice is mentioned in this application it will be understood that this includes a discharge device which is filled with one or more vapors or with a mixture of gas and vapor.

In the drawing accompanying and forming part of this specification several embodiments of the invention are shown in which,

Fig. 1 is a schematic view of an electric discharge device having two thermionic electrodes and a circuit therefor,

Fig. 2- is a similar view of an electric discharge device having a thermionic cathode and a cold anode and a circuit therefor,

Fig. 3 is a similar view of two discharge devices each having two thermionic electrodes and a circuit therefor,

Fig. 4 is a similar view of an electric discharge device with a thermionic cathode and I two cold anodes and a circuit therefor, and

Fig. 5 is a similar view of an electric discharge device with two thermionic electrodes and a circuit therefor.

Referring to Fig. 1 of the drawing, 1 indicates a gas filledelectric discharge device. The gas filling is, for example, argon at a pressure of 2 mm. to which is added a quantity of mercury. in the device 1 are located two thermionic electrodes 2 and 3 which consist of a coiled wire, such as tungsten, covered with a layer of material with high electron emission characteristics such as a layer of earth alkali oxide, barium oxide, for example. The thermionic electrodes are connected to the secondary coils l and 5 of a transformer. The right side of the primary coil 6 of said transformer is connected to the thermionic electrode 2, while the left end is connected to one of the terminals of the alternating current source 7. The other terminal of said current source 7 is connected to the thermionic electrode 3. It is self-evident that these connections to the thermionic electrodes 2 or 3 can also be made at any point of the electrode circuit, for instance, at the center of the coils 4 and 5.

When current is applied to the circuit a glow discharge develops immediately between the electrodes 2 and 3. The glow dis-- charge current then flows through the primary coil 6 of the transformer with the result that alternating currents are generated in the secondary coils 4 and 5, which heat the thermionic electrodes 2 and 3 to the temperature required for electron emission. The type of discharge is thus changed by the large electron emission and an arc discharge is developed in the vicinity of the electrodes 2 and 3 while the remaining part of the discharge tube 1 shows a positive column.

Where the distance between the electrodes or other conditions are such that the discharge current which fiows through the device is too low to induce sufficient current in the coils 4 and 5 the starting of the discharge in the device is facilitated by short-circuiting the discharge device. A connection for this purpose is indicated in Fig. 1 by the dotted line 8. When the switch 9, in lead 8, is closed the discharge tube 1 is short-circuited so that a high current flows through the transformer coil 6 with the result that the thermionic electrodes 2 and 3 attain the required electronemitting temperature ina very short time. lVhen switch 9 is open-circuited the electric discharge is established between said electrodes 4 and 5. Where desired, switch 9 is actuated by automatic means, as a bimetallic strip, controlled by the temperature of said electrodes 4 and 5.

The primary transformer coil 6 is of such dimensions that it serves as stabilizing impedance for the discharge tube. A large part of the energy absorbed in this impedance is converted into the heating currents for the thermionic electrodes so that this energy is utilized to advantage. Moreover, no separate primary coils for the supply of the heat ing current are required which is a saving of material to reduce the costs of manufacture.

The discharge device 10 shown in Fig. .2 has only one thermionic electrode 11 which is heated by means of the secondary coil 12 of a transformer, the primary coil 13 of which is connected in series with the discharge device 10. The discharge device 10 has a cold anode 14. Current flows through winding 13 only during half of each alternating current cycle. This interrupted direct current induces a sufficient secondary current in coil 12 to heat said cathode 11 to an electron emitting temperature.

In Fig. 3, two electric discharge devices 15 are connected in parallel. Each of said devices is provided with two thermionic electrodes 16 and 17. The electrodes 16 are heated by means of a transformer which is connected in the manner described in connection with Figs. 1 and 2. The electrodes 17 are connected together and in series with the secondary coil 18 of the transformer 18, 19. When desired the electrodes 17 are connected in parallel. A single transformer thus suffices for heating both of said electrodes 17.

In Fig. 4, an electric discharge device 20 with the thermionic cathode 21 and a pair of anodes 22 and 23, is illustrated. The discharge device 20 is operated by means of a transformer with a primary coil 24 and a secondary coil 25. The anodes 22 and 23 are connected to the ends of the secondary coil 25, and the transformer coils 26 and 27 are connected between said anodes 22 and 23 and said coil 25. These coils 26 and 27 are wound on two cores of a three-coretransformer. The secondary winding 28 is wound on the third core, and the ends of said coil 28 are connected with the current supply wires of the thermionic cathode 21. This thermionic cathode 21 is connected to the center of the transformer coil 25 by conductor 29. The transformer coils 26 and 27 are wound in such manner that during that half cycle of the alternating current during which the current flows through coil 26, the lines of force have the direction indicated in Fig. 4; by a full line, while during the half cycle during which the current flows through the coil 27, the direction of the lines of force is reversed, as indicated by a dotted line in Fig. i. As a result, an alternating potential is induced in the secondary coil 28 which potential heats the thermionic cathode 21. A glow discharge takes place between the cathode 21 and the anodes 22 and 23 when the electric discharge device is connected to the current source, the glow discharge current flow causes a current in the secondary transformer coil 28 which heats the cathode 21 to an electron emitting temperature of such a degree and an are discharge, accompanied by a positive column is created in said device 20. The stabilizing impedances in this circuit are the primary windings 26 and 27.

The discharge device 30 shown in Fig. 5 is provided with two indirectly heated electron emitting electrodes 31 and 32 which are of the equi-potential Hull cathode type. The electrode, 31 is directly connected with one terminal of the alternating current source 33, while the electrode 32 is connected to the otherterminal of said current source through the primary transformer coil 34:. The heating means 35 of the indirectly heated electrodes 31 and 32 are connected in series and are also connected in series with the secondary transformer coil 36. A glow discharge takes place between the cathodes 31 and 32, and said electrodes are covered with sharp points which are formed, for example, by a layer of electron emitting material such as the stabilizing impedance for the barium oxide to facilitate the establishment of said glow discharge. The primary transformer coil 34 acts as a stabilizing impedance.

Although I have shown and described and have pointed out in the annexed claims certain novel features of the invention, it will be understood that various omissions, substitutions and changes in the several steps of the method and in its operation and in the forms and details of apparatus involved and the preparation thereof may be made by those skilled in the a t without departing from the spirit of the invention, for example, the electric discharge devices are, when desired, of various shapes, the discharge is restricted to a positive glow discharge for advertising and similar purposes, when desired, the tubes are then shaped as letters and have a considerable length, and the invention is applicable to electric discharge devices for rectifying alternating current.

What I claim as new and desire to secure by Letters Patent of theUnited'States is 1. In combination an electric discharge device comprising a container, agaseous atmosphere therein, electrodes sealed therein, at least one of said electrodes having high electron emission characteristics when heated and a circuit for said device comprising a transformer, the primary of said transfornr er being connected in series with the discharge path in said *device and serving as discharge in said device, the secondary of said transfornier being connected to said thermionic electrode and adapted to supply the heating current for said electrode.

2. in combination an electric discharge device comprising a container, a gaseous atmosphere therein, electrodes sealed therein, at least one of said electrodes having high electron emission characteristics when heated and a circuit for said device comprising a transformer, the primary of said transformer being connected in series with the discharge path in said device and serving as the stabilizing impedance for the discharge in said device, the secondary of said transformer being connected to said thermionic electrode and adapted to supply the heating current for said electrode and means connected in parallel with said device to short-circuit said device when said electrode is cold.

3. In combination two electric discharge devices comprising a container, a gaseous'atmosphere therein, electrodes sealed therein, said electrodes being electron emitting when heated, and a transformer adapted to supply the heating current to one of said electrodes in each of said devices and another transformer, the primary of said second named transformer being connected in series with said device and serving as the stabilizing impedancefor the discharge in said device, the

secondary of said second named transform er being adapted to su ply the heating current to the other of sai electrodes in each of said devices.

4. In combination an electric discharge devicecomprising a container, a gaseous atmosphere therein, a cathode and two anodes sealed therein, said cathode having high electron emission characteristics when heated and a circuit for said device comprisingva transformer, the secondary of said transformer being connected to said anodes, another transformer connected oetween said anodes, another transformer connected be-' tween said anodes and the secondarjy of said first named transformer, the primary cells of said second named transformer serve as the stabilizing impedance for the discharge in said device and the secondary coil of said second named transformer supplies the heating current for said cathode.

In witness whereof, I have hereunt hand this sixth day of July, 1932.

GUSTAV ZECHER.

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